4AGE Head and Block Decking

[jak]

Hey guys.

i have an ae71 with a bigport 4age. I also hav a spare which i have pulled down and ported out to somewhere close to formula atlantic specifications and i am about to send it off to get cleaned, guides cut etc etc and i am thinking i want to go to a pretty high comp ratio to get this thing moving along.

My question is, what is the absolute MAXIMUM that i can shave this thing. Im not to worried about interference if the timing belt snaps it wouldnt be that much of a problem if the valves hit the pistons as it would give me a reason to rebuild the bottom end.

with a bit of luck im hoping to reach more than a 12.7:1 CR

but yeh, wats the max?

Im also considering decking the block while im at it which would help a bit more so wat would be the max i could deck the block with the standard GE pistons and max head shave?

Cheers
Jak

[Ben Wilson]

I never cc'd it, but this is as far as I've seen one taken.



I think we took about 1.5mm off. It's assembled now and the valves didn't come anywhere near the pistons when I dummied it up.

Gotta get back out to the shed and finish it one day....

[jak]

ahh awsome.

geez if thats 60thou i wonder how far it can go seems to be a bit more left in it. especially with valve clearances and such.

Cheers
Jak

[takai]

Ive done 50thou easily. Became an interference engine.... or that could have been the 480thou lift.

[oldeskewltoy]

A lot depends on other parts.... What headgasket will you be using? What piston will you be using? Also how much chamber work have you done......

[jak]

will be using wiseco pistons, TRD 0.5mm headgasket and alot of chamber work. more than the formula atlantic engines. and 2mm oversize valves.

Cheers
Jak

[abently]

I guess if you get a cut-away picture of the head, you can get an idea of how much you can safely shave without the risk of warping from reducing the integral strength of the head.

I've done 1.5 easily (non Toyo head) and think 2mm would be possible but cutting it fine as the factory decks I seen seem to be around 7mm in thickness for the 4cyl heads.

With your CR, I tend to use OEM cam timing and static CR along with recommeded fuel octane to come up with something that won't ping at full load. From what I remember, unless your using a 280+ deg camshaft (11.0 static CR doable), I personally would keep to somewhere around 10.5.

I can explain how I get my numbers if you would like to put it to the test.

[jak]

its going to be a full race N/A 4age running as bigger camshaft as i can find probably somwhere around a 315 deg. will hav aftermarket engine management and adjustable cam gears.

from what i can see in Ben Wilsons pic the main problem will be the valves not seating properly if i take it to far. will probably be needing more than 11:1 CR now that i think of it. as im heading for the 250-300hp mark with a natural 4a.

[abently]

315+ deg will definitely need more then 11:1 to maximise efficiency.

You may be able to find off the shelf forged pistons with enough dome to possibly leave the head standard. I remember a german company did 12.4:1 3SGE pistons so I dare say with such a popular Engine as the 4A, that even Wiseco and CP should have custom designs in their database for you.

And therefore keep the Head (and investment) performance reliable for you long term.

EDIT: Found them and your in luck they do the 4A and at a nice 11.8:1

You might not even have to shave it at all after calculating the real CR from the reduced Head CC and 0.5mm gasket.

http://wossneronline.com/Toyota.php

$550US

[fixeruperer]

300hp na 1.6 is a massive ask.
formula atlantic trd had all the money and the smarts and ended up with around 240hp@8500rpm with a c/r of 12.7:1.

[jak]

yea wiseco make a high compression piston but im looking to get the biggest possible doing all the modification possible. Like everything that can be done to get a higher cr will be i was planning on hig comp pistons and a shaved head and everything, the whole number. I would like to achieve the higest comp ratio possible with a 4age.

fixeruperer: im boreing it 40thou and will be stroking it to the max possible with the combo i end up with so i will hopefully be closer to 2L.

abently: those pistons look like the go and there not to overpriced either. i would be keen to use them, but i would also like to get the CR out to the absolute max possible. 12.7:1 on the formula atlantic but with a bit of work i think i might be able to get it up abit higher. i was thinking something along the lines of ATTKD or SPOOL conrods off ebay because this is not a turbo application so they would not be the weakest link.

Cheers
Jak

[fixeruperer]

ah ok, that will help , sleeve it and bore it further to keep it over square so you can rev it.

[jak]

ahh i never thought of sleeving it brilliant idea. Is that an expensive process these days?

Cheers
Jak

[fixeruperer]

depending on what sleeves you get (brand and type) around $150-$350 (inc sleeve) a cylinder.
ask your machinist what he charge's.

ive havent yet sleeved a 4ag so i dont know what the average price for a 4a sleeve is.

[Ben Wilson]

Sleeving a 4AG won't be easy, the cylinders are very close to each other..

I'm not a big fan of 'pop top' pistons, they don't leave a nice combustion chamber shape. From a theoretical point of view, milling the head could be a better way to go than high compression pistons, it gives you more quench area and a cleaner chamber.